Peak flow trends highlight emerging urban flooding hotspots in Texas

By Matthew D. Berg

Peak flow trends highlight emerging urban flooding hotspots in Texas

In the aftermath of flooding disasters, a temptation is to pursue recovery while also dismissing the event as unlikely to recur. Is it possible that underlying streamflow trends, which often avoid detection, help explain individual flooding episodes and should influence future expectations? How do impoundments (dams) affect these trends? Our study provides a comparative analysis to answer these key questions that help determine whether flood planning will be successful. Examining the 25 largest Texas metropolitan areas, we assessed peak flow trends for stream gages having at least 25 years of data. Of 181 total gages, 34 (18.8%) exhibited significant upward trends. Over 85% of those with upward trends are located in the Dallas-Fort Worth-Arlington (17.6%) and Houston-The Woodlands-Sugar Land (67.6%) areas. Approximately 62% of gages with upward trends are in Harris County. Among 84 sites impacted by impoundment, 11 (13.1%) still exhibited upward trends. These findings show that increasing peak flows underlie recent flooding in some areas, spotlighting streams in greatest need of examination. Increasing peak flows in some locations even after impoundment suggest dams might not be a complete solution. Finally, maintaining a robust monitoring network is critical to flood planning, and analysis is hampered when data are lacking.